The present invention relates generally to the joining of the ends or edges of one or more pieces of material, and more particularly to a method and apparatus for joining the ends of a muffler shell to produce a sound mechanical joint having an aesthetically pleasing appearance.
Various methods have been employed to join two pieces of material together in current manufacturing and assembly technologies. For instance, welding and mechanical joining are typically employed for joining pieces of sheet metal together, especially the ends or edges thereof.
In conventional muffler assembly, a piece of sheet metal is typically wrapped around a muffler assembly, thereby encapsulating and supporting the internal components. The sheet metal is welded or mechanically joined together at its respective ends to form a seam.
While welding structurally provides a sound method of joining the respective ends of the sheet metal together, this method fails to provide an aesthetically pleasing appearance for the resulting muffler. As such, manufacturers are typically required to provide a second housing (e.g., a cover or wrap) over the sheet metal cover to hide the unsightly weld marks on the sheet metal.
Therefore, there existed a need in the relevant art to provide a method of joining two ends of sheet metal in such a way as to provide a sound structural joint which is also aesthetically pleasing. Examples of joining techniques can be found in U.S. Pat. Nos. 4,513,596; 4,567,742; 4,864,712; 4,924,684; 5,049,424; 5,105,639; 5,193,374; 5,247,521; 5,692,300; 5,860,305; 5,943,891; and 5,980,744, the entire specifications of which are incorporated herein by reference.
One method used to join respective ends of sheet metal involved the use of a lock seam. The lock seam method employs forming the respective ends into an interlocking set of folds which cooperate to maintain the two respective ends joined. While this method does provide an aesthetically pleasing and structurally sound joint, its creation requires force to be applied on the joint in a direction toward the muffler body. However, the internal components of the muffler provide little or no support to most of the cover area of the sheet metal. As such, application of this type of joint causes deformation and damage to the cover of the muffler.
A further concern with respect to lock seams is their structural integrity. Commonly, these seams incorporate a series of flat folds which provides room for lateral movement of the respective ends in the seam, thereby weakening the joint.
In view of the above, it would be desirable to provide a method and apparatus for manufacturing a lock seam that is mechanically sound and also aesthetically pleasing, but does not require force to be applied in a direction toward the body of the muffler when it is formed.
In view of the above, it is an object of the present invention to provide a method for forming a lock seam which does not require force to be exerted in a direction toward the body to be sealed.
It is a further object of the present invention to provide an apparatus for forming a lock seam which provides a structurally sound joint that is also aesthetically pleasing to view.
In accordance with the broad teachings of this invention, a method and apparatus for manufacturing a lock seam having an advantageous construction is provided. The lock seam for joining a first edge of material to a second edge of material has the first edge wrapped in a first curl such that the first curl is substantially circular in shape. The second edge is wrapped in a second curl which is also substantially circular in shape. The inside surface of the first curl is wrapped about said outer surface of said second curl.
In a further aspect of the present invention, a pressureless lock seam is utilized in conjunction with a muffler. By the term xe2x80x9cpressurelessxe2x80x9d as that term is used herein, it is meant that the lock seam is formed without the application of any substantial amount of pressure directly toward the body to be sealed (i.e., perpendicular to the body). The lock seam of the present invention is formed by the application of forces that are substantially parallel to the body to be sealed. The muffler has a muffler canister, an inlet head/bushing and an outlet head/bushing positioned on opposite sides of the canister. An outer wrap is provided which encapsulates the canister. The outer wrap is positioned flush against and extending around the periphery of the inlet head/bushing and the periphery of the outlet head/bushing. The outer wrap is then joined by a lock seam produced in accordance with the general teachings of the present invention.
In accordance with one embodiment of the present invention, a method for forming a seam is provided, comprising:
providing a sheet having spaced and opposed first and second edges;
providing an object to be encapsulated by the sheet;
positioning the object on the sheet parallel to the first and second edges;
manipulating the first and second edges towards one another so that the surfaces of the first and second edges contact one another in a substantially flush manner so as to form a flange-like projection, wherein one edge extends past the other edge;
manipulating the flange-like projection so as to form the seam, wherein the seam comprises the first edge wrapped in a first curl and the second edge wrapped in a second curl, the first curl being substantially circular in shape and the second curl being substantially circular in shape, wherein an inside surface of the first curl is wrapped about an outer surface of the second curl.
In accordance with another embodiment of the present invention, a method for forming a seam for a muffler is provided, comprising:
providing an outer wrap having spaced and opposed first and second edges;
providing a muffler canister to be encapsulated by the outer wrap;
positioning the muffler canister on the outer wrap parallel to the first and second edges;
manipulating the first and second edges towards one another so that the surfaces of the first and second edges contact one another in a substantially flush manner so as to form a flange-like projection, wherein one edge extends past the other edge;
manipulating the flange-like projection so as to form the seam, wherein the seam comprises the first edge wrapped in a first curl and the second edge wrapped in a second curl, the first curl being substantially circular in shape and the second curl being substantially circular in shape, wherein an inside surface of the first curl is wrapped about an outer surface of the second curl.
In accordance with still another embodiment of the present invention, an apparatus for forming a seam from spaced and opposed first and second edges of a sheet for encapsulating an object is provided, comprising:
a selectively operable system for manipulating the first and second edges towards one another so that the surfaces of the first and second edges contact one another in a substantially flush manner so as to form a flange-like projection, wherein one edge extends past the other edge; and
at least one other selectively operable system for manipulating the flange-like projection so as to form the seam, wherein the seam comprises the first edge wrapped in a first curl and the second edge wrapped in a second curl, the first curl being substantially circular in shape and the second curl being substantially circular in shape, wherein an inside surface of the first curl is wrapped about an outer surface of the second curl.
In accordance with still another embodiment of the present invention, an apparatus for forming a seam from spaced and opposed first and second edges of an outer wrap for encapsulating a muffler canister is provided, comprising:
a selectively operable system for manipulating the first and second edges towards one another so that the surfaces of the first and second edges contact one another in a substantially flush manner so as to form a flange-like projection, wherein one edge extends past the other edge; and
at least one other selectively operable system for manipulating the flange-like projection so as to form the seam, wherein the seam comprises the first edge wrapped in a first curl and the second edge wrapped in a second curl, the first curl being substantially circular in shape and the second curl being substantially circular in shape, wherein an inside surface of the first curl is wrapped about an outer surface of the second curl.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.